This invention relates to transmissions of the compound type, which are comprised of main as well as auxiliary or "piggyback" units. More particularly, this invention relates to apparatus for jointly interlocking such units by means of a single control apparatus, typically a range or auxiliary shift rail, which extends from within an auxiliary gearbox unit to and within a main gearbox unit.
Dimensional constraints generally dictate where and how various gears and shift rail apparatus are placed and oriented respectively, within a single transmission unit. When compound transmissions involving multiple gearbox sections are employed, the dimensional constraints become greater, thus more critical particularly as to those elements within one gearbox unit which must interface with elements in an adjacent unit. As this invention relates specifically to shift rail and associated interlock compatibility, the dimensional constraints pertinent thereto could be greatly relaxed if the range shift rail did not have to be positioned so as to be "in-line" with the main gearbox shift rails. Thus, greater flexibility would result if the range shift rail were more easily accomodated when offset or asymmetrically positioned with respect to main gearbox shift rails, thus making more auxiliary gearboxes compatible for assembly with greater numbers and varieties of main gearbox units.